Variable inductance units



1933. J. A. WILLOUGHBY 1,896,269

VARIABLE INDUGTANCE UNITS Filed Jan. 19, 1929 I: can... 4

67% A INVENTOR. 0 2z 8 y zflm ji ATTORNEY Patented Feb. 7, 1933 JOHN A. WILLOUGHBY, OF CAMBRIDGE, MASSACHUSETTS VARIABLE INDUCTANCE UNITS Application filed January 19, 1929. Serial No. 333,704.

My invention relates broadly to electrical inductances and more particularly to induc tances in the form of torus coils.

One of the objects of my invention is to provide a compact variable inductance unit.

Another object of my invention is to provide a compact variable inductance un t which has substantially no stray magnetic field and is suitable for use in gang controlled systems.

Still another object of my invention is to provide a compact variable inductance in which the circuit is always complete when the value of inductance is varied.

Other and further objects of my invention will be apparent to those skilled in the art to which this invention pertains from the following specification and the annexed claims.

I ductance unit whereby certain turns of the inductance unit are rendered ineffective and the total inductance of the unit is varied.

Referring to the accompanying drawing,

Figure 1 illustrates a View in side elevation of a preferred embodiment of my invention;

Fig. 2 illustrates a cross-sectional view along the lines 2-2 of Fig. 1; Fig. 3 is a side elevation of the variable inductance unit of my invention in the effective position and Fig. 4 is a view in side elevation taken on line 44 of Fig. 1 of the form of my invention when all the turns of the inductance are rendered ineffective.

Referring to Figure 1 of the drawing in detail, reference numeral 1 designates a circular frame member of insulating material, such as vitreous materials or phenol condensation products. This member may consist of a tubular member of insulating material. Support 2 is provided for supporting the frame member. Winding 3 of electrical conducting material is provided about the frame 1. A hub member 16 is carried by the frame or core 1, through arm 8. Hub member 16 has a bushing 15 which is internally threaded and engages threads 1 1i on shaft 14.

Shaft 14 carries a resilient radial arm 13' which at its outer end carries integrally a resilient conducting plate member 13. Shaft 14 is provided with knob 4. Resilient plate member 13 is positioned to make contact with turns of winding 3 as shaft 14 rotates, and as shown, it is advantageous to make resilient plate member 13 of approximately annular arc shape but tapered in width from a relatively wide portion adjacent arm 13 to a relatively smaller width at its end, so as to approximate spiral shape. The tapered plate can be rotated to gradually short circuit the turns of the winding precision. It is also advantageous to slightly spring resilient plate member 13 so that its outer periphery is a helix. The makin of a resilient and certain contact is thereby facili- 7o tated.

The element 13 is rotated by the knob 4 and brought into engagement with successive turns of the inductance unit, through the action of the threads 14' on the shaft 14; (Fi 2) which engage complementary threa s on the bushing 15. Member16 supports the bushing 15 in position with respect to the frame member 1. Connection A is made to shaft 14, and connection B is made to winding 3. As the knob 4 is rotated the member 13 engages successive exposed turns of the inductance unit until it short circuits and renders ineffective any part or all of the turns of the unit as shown in Fig. 4. B

y reversing the directlon of rotation of the knob 4 the resilient member 13 is gradually brought out of engagement with certain of the turns until substantially all of the turns of the unit are effectively in circuit as illustrated in Fig. 3.

By providing a core of magnetic material an inductance unit of comparatively high inductance may be made, in which case many layers of turns may be provided instead of just one layer. A readily variable inductance unit having an inductance of several henries may be thus obtained for use in filter circuits, such as are commonly employed in conjunction with alternating current rectifiers.

Short circuiting of the turns of the induc- 3 with a high degree of 65 tance not in use is particularly advantageous especially where the inductance is employed as a high frequency choke coil. Oscillatory circuits in which oscillating currents of large magnitude are developed are prevented by short circuiting the individual turns of the unused portion of the choke coil. Shafts having gears or pulleys for gang or remote control of a plurality of inductance units simultaneously may be provided for the inductance units in place of the knobs 4:;

While I have described my invention as embodied in several modified forms I desire it to be understood that other modifications are possible and that I do not intend that my invention shall be limited in scope to the embodiments described in the foregoing specification but only by the scope of the appended claims.

WhatI claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In a variable inductance, an annular core member, an inductive winding wound on said annular core member, a central hub internally threaded and carried by said an nular core member, a rotatable shaft coaxia with said annular core member and carried by said hub, said shaft being provided with threads adapted to engage the threads of said hub, a resilient conducting plate member carried by said shaft and adapted to make electrical contact with individual turns of said winding in a plane substantially normail to said shaft, said resilient plate member being angularly disposed so that its outer edge is subsantially helical, whereby the rotating advancement of said shaft in screw relationship with said hub causes the turns of said inductance to be selectively short circuited.

'2. In a variable inductance, an annular core member, an inductive winding wound on said annular cor-e member, a central hub internally threaded carried by said annular core member, a rotatable shaft coaxial with said annular core member and carried by said hub, said shaft being provided with threads adapted to engage the threads of said hub, an arm extending radially from said shaft, a conducting spiral plate member integrally connected with said arm and disposed approximately normal to said shaft, said spiral plate member being tapered in width from a relatively considerable width adjacent said arm to a relatively small width at its end, and being adapted to make electrical contact with individual turns of said winding'in a plane substantially normal to said shaft, whereby the rotating advancement of said shaft in screw relationship with said hub causes the turns of said inductance to be selectively short-circuited.

3. In a variable inductance, an annular core member, an inductive winding wound on said annular core member, a central hub internally threaded carried by said annular core member, a rotatable shaft coaxial with said annular core member and carried by said hub, said shaft being provided with threads adapted to engage the threads of said hub, an arm extending radially from said shaft, a conducting spiral plate member integrally connected with said arm and disposed approximately normal to said shaft, said spiral plate member being tapered in width from a relatively considerable width adjacent said-arm to a relatively small width at its end, and being adapted to make electrical contact with individual turns of said winding in a plane substantially normal to said shaft, said spiral plate member being slightly sprung so that'its periphery is a helix of small angle, whereby the rotating advancement of said shaft in screw relationship with said hub causes the turns of said inductance to be selectively short-circuited.

In testimony whereof I affix my signature.

JOHN A. NILLOUGHBY. 

